By default when you're making a new event the iPhone lets you set the time in five-minute increments, but if you want to get a bit more granular, Finer Things in Tech points out you can simply double-tap the time picker to one-minute increments.

When you're in an app like Calendar, just double-tap the time picker and it'll change between one minute and five minute increments, which should prove helpful for all those very specific meetings you have planned throughout the day.